Motor vehicles having an internal combustion engine typically include an evaporative emission control system which serves to reduce fuel vapor emissions. Such systems include a vapor collection canister having carbon or other material which serves to absorb fuel vapors that are generated within a motor vehicle fuel system. A canister purge valve is located between the canister and an engine intake manifold. The canister purge valve may be opened or closed to either place the canister in fluid communication with the engine intake manifold or to isolate the canister from the engine intake manifold, respectively. The canister is also connected to a vent solenoid valve which serves to place the canister in fluid communication with atmospheric air and to isolate the canister from atmospheric air.
Under the appropriate conditions, the canister is purged so that fuel vapors collected within the canister do not undesirably escape into the atmosphere. This is done by opening the canister purge valve and the vent solenoid valve, thus enabling vacuum generated by the engine to draw in atmospheric air through the canister and then draw out the fuel vapors from the canister as part of a process for purging the canister. The fuel vapors are then used in the normal combustion process. Alternatively, the vent solenoid valve is closed to isolate the canister from atmospheric air. This enables the performance of a selected on board diagnostic procedure for detecting whether there is a fuel vapor leak in the system that is above a predetermined level.
Conventional canister purge and vent solenoid valves include a solenoid and spring arrangement for moving a valve element between open and closed positions. During operation, the solenoid is energized so as to move the valve element to a desired position. The spring serves to return the valve element to its initial position when power to the solenoid is removed.
However, the use of such valves increases the amount of components needed and thus increases manufacturing and other costs. Therefore, there is a need for valves having a reduced number of components and which cost less to manufacture and assemble.